


in pursuit of your deepest urge

by bokutoma



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Angst, Angst and Porn, Catholic Guilt, F/M, Female My Unit | Byleth, Healing, Introspection, Major Spoilers, Porn with Feelings, Self-Flagellation, Spoilers, except it's the church of seiros, oh boy, seriously do not read if u don't know The Lore, seteth is fucking horny, vague phantom elements
Language: English
Status: Completed
Published: 2020-01-07
Updated: 2020-01-07
Packaged: 2021-02-24 16:34:29
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,175
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22161016
Author URL: https://archiveofourown.org/users/bokutoma/pseuds/bokutoma
Summary: seteth will never forgive himself for his many transgressions; his feelings for byleth are just the latest sin
Relationships: My Unit | Byleth/Seteth
Comments: 19
Kudos: 129





	in pursuit of your deepest urge

**Author's Note:**

  * For [beastprince](https://archiveofourown.org/users/beastprince/gifts).



> this is a commission for ray!! i love u <333

It's a grave day when Seteth has to concern himself with tasting the flames of Ailell.

It's not his fault, and yet these feelings can be attributed to no other cause. The temptations of youth should be far behind him, buried with an insurmountable number of years and a love that has calcified in the hollow where his heart should be. Instead, a bit of that hellfire stirs in the pit of his stomach where old draconic instincts now hibernate.

Professor Byleth is temptation incarnate, and still, Seteth knows that his indecent feelings have nothing to do with any provocations on her part, only the foolish whimsy of a sad old man. He should be stronger; at the bare minimum, he should be able to silence the instinct that demands he pant after her, sink his claws into her. He's not yet done his penance, not yet suffered enough for failing to protect what he'd sworn to hold above all else all those ages ago.

When his gaze strays to the planes of her toned stomach, to the ill-concealed flesh of her thighs, he pays homage to the old ways. Perhaps on a general level, he is glad to see the teachings of Seiros softened by that self-same hand, but he is branded as a _saint_ , should be held to a higher standard as such, and regardless...the punishment should fit the crime.

 _Cichol_...

The name eats at him like a beast drawn to rotting flesh, but regardless, he longs to hear it from rosebud lips. The sting of the lash as he conducts his own private confession is not enough to dislodge these thoughts permanently, no matter the strength he wields. He should be concerned, he knows; _Saint_ Cichol is hardly worthy of that title with impure wants, no matter how pious the facade he maintains seems to be. Instead, all that resides within him is a numb sort of desperation, the eagerness of a subhuman creature, wishing to paw and lick and rut.

 _Byleth_...

She is a lovely thing; she is the warmest person he has had the fortune to know in many lifetimes. There is nothing of the old ways ingrained into her, no memories of a misremembered age, but when she fights, eyes aglow with passion and body streaked with blood, he feels something ancient and primal stir within her (and it is wondrous and terrible both).

Even at his lowest, Seteth refuses to degrade or defile the thought of her. He cannot fault her for a curse of the flesh he is too weak to overcome, nor can he selfishly use her to put balm on a festering, self-inflicted wound.

Still, he cannot halt an obsession with pretty words or the noblest of ideals. His eyes track her with a hunger he had thought himself to have long outgrown, lingering much in the way of adolescents. It might have been humorous if it weren't quite so damning. Now, too, she is like them, like those of his kind, with hair of softest green and eyes that have learned to smile. The ache quickens at the memory of an age-old craving, and no matter how he tries to stifle feeling and cut it off completely, he longs to take her in hand only to take her apart.

She is crafted as a test of his will, he who should know better than to attach himself to mortal things, he who should remember his failings before they are honor-bound to repeat themselves.

Modesty makes a joke of him.

He remains lucky that he's used to watchfulness, to tracking a thousand possible dangers at once, or he would have been caught months before. Like this, he can track the flex of muscle and the shift of delicate and calloused skin both. Byleth's thighs are a beacon for a starving man, a lighthouse that's half mirage, a haven that's driving him to madness. There is a veneer there, but so much is revealed already with patterned fabric. All at once, it's too much and not enough, and Seteth longs with a fierceness he tries to carve from himself on a daily basis.

He tries the paddle, studded with cold, bitter metal. Even as it eats at his flesh with biting hunger, it doesn't help.

With his sin, he makes a mockery of the monastery, of the life he has tried so carefully to craft. Still, he has limits, and though he has made himself into a poorly performing jester, there are lines he has not yet crossed, parts of himself he has not yet blackened with tarnish.

A life of chastity is punishment and reward both. The work he does here, shaping young minds into able fighters, it's more than he deserves, and Flayn is a blessing he has yet to earn.

No sacrifice is too great to maintain this, even if the madness of a thousand years and one single moment plays with the fraying control he has left.

Then war comes to Fódlan.

It should revolt him - it does, all this needless death that pants even the corners of the continent with iron - but in many ways, it comes as a relief. Byleth is gone, and though he knows they will need her, that magnetism she wields so unknowingly, to survive this, it grants him waking asylum.

His nights are still plagued by thoughts of her, though. It's to be expected, of course; haunting memories do not disappear because one asks them to. Would that all his dreams were depraved, though, because self-loathing and disgust are far easier to bear than whatever this has become, visions of nothing more than gentle touches.

For a saint, he has always found that a hand to the cheek is easier to bear when it strikes rather than caresses.

Not for the first time, he envies Flayn. It's a ridiculous thought, some people would believe, the idea of being jealous of the virtue of one's own child. These humans he's lived among, they believe in the solemn superiority of a parent's experience, that piety comes from a knowledgeable head.

They are right, and they are wrong.

Saint Cethleann the Nabatean is by no means unknowledgeable, for she has lived almost as long as he. To imagine that a child cannot surpass their parentage, however, is nothing short of laughable, especially considering all that his dear daughter is.

If there is one thing that Seteth (that Cichol, long dead and buried as he is) can be proud of, it's that his daughter will never know what it is to be such a wretch such as he.

Then Byleth returns.

Five years without the sight of her, and he had not yet forgotten a detail of her face. What a miserable man he had thought himself, but at least he can be certain that she is the real thing, and not a slithering specter.

Every fiber of his being is put to necessary use restraining himself from lunging for her and never letting go, feral and yet desperately protective. There are others she must be looking for, lost as she must be feeling.

(He can read it in her eyes. When had he allowed this to get so far, to turn from the memorization of her form to that of her mind?)

It is to him that Byleth turns.

From there, it escalates faster than Seteth can put a stop to, faster than starry scars can sprout on his skin, It rises like a fever, like the illness that it is, and he cannot claw it from his skin any more than he wants to.

What a thing it is to taste the cloying sweetness of possession.

Fathomless depths in her eyes call to the dragon of him, dare him to swoop and soar and plunge into the heart of her, to nest in her marrow. He cannot give in, cannot tempt himself into such sweet, ecstatic damnation. Absolution and poison both taste like wine, after all, and this is something he knows far too well. There is a war outside the monastery gates, ancient evil and hereditary enemies that leak past their defenses.

He is Saint Cichol, pious and devoted to family and cause alone. Nothing can sway him from his course.

He is Seteth, a not-quite man, with fangs and a whiplike tongue, and he is all too weak to the love in her eyes.

Recorded history will not be able to say that he didn't break, only that he didn't break first.

Lustful thoughts and unconscious fantasies be damned; she is devouring him, hands everywhere, coaxing and uncloaking in that naively skillful way of hers. No one should be good at everything, but there's something to the theory that stopping Byleth is an impossibility.

To be buttoned up has been both the right path and a defense both. She makes him a fool again, and his shirt is gone before he can even raise his trembling hands to meet her, to seek somewhere safe (or _licentious_ ) to land.

Byleth catches them in her own, and a lump forms in his throat.

_You should know better, you old lech. You are a convenience, and this burden is yours to bear, penance for breaking your chastity._

Then she brings them to her hips, and he is saved.

He is frantic now, desperate like a man centuries his junior, and every part of him is aflame and angry with a haze that should alarm him - he has not felt so much in years.

It matters not. Seteth is past the point of no return, and if his grasping, clawlike hands leave bruises, so much to remember what has happened here, every sordid moment etched into flesh and memory both. The thin material of Byleth's tights run and split along the pads of his fingers, and finally, _finally_ , skin meets skin.

What happens to the rest of her clothes, he does not know, so lost is he in mist and future memory, but the brush of her fingers as she peels his pants from him, unwraps him, unravels him, is a shock and sensation he cannot be distracted from. The lightning that had lanced through him at the barest meeting had been manageable when he'd initiated, intentionally or otherwise, but here, nothing to protect or defend him, he is lost so consummately that knows he will never wake up again.

"Byleth," he groans when she takes him in hand. She is not gentle, but neither is her roughness meant to torment. _Eager_ is perhaps the aptest description, and that alone is enough to snap the fraying tendrils of self-control that he had managed to grasp hold of and send him spiraling.

Her mouth shapes his name with soundless pleasure as he tugs her up to him, up to his biting, frenetic mouth, and works her open with the ease he had once thought lost to him forever. She keens, eyes half-lidded and so thrillingly familiar, and he swallows it more greedily than he's claimed anything in more than an age.

She does not touch, and yet he finds himself flayed open more effectively than any instrument of torture he has made himself familiar with.

"Byleth," he prays against her neck, pressing a kiss better suited for a brand to the tender skin there. Everything about her is warm and soft, his heartless angel, and she is unbelievably slick. Perhaps it makes him a loathsome, base creature, but this is what reassures him of her want. Flowery speech has never done much to quiet a rampaging beast, and she has never been one to speak at all.

When she starts to babble (more words than he's ever heard from her at once, and he hoards them with gluttonous glee), beg for his cock in her, he can do nothing but oblige.

He is clumsy; he is centuries unpracticed, and he slips against her, unsure how to make the rightful connection. She remains wanting anyway, and when he slides home, they fit together better than he ever could have imagined.

 _Oh_ , the things he has imagined.

"Byleth," he stutters in time with the dual movement of their hips, and he wants to check the places where his hands have been, her breasts, her back, her thighs - those damnable thighs - to ensure he hasn't tarnished them. He finds his gaze unmoved from the clouded, half-seeing allure of her own.

They find release, one bleeding into the other, and only then can Seteth bring himself to see the results of his flaming hands.

Perhaps unsurprisingly, she remains unmarked, only old scars there, littered across her like celestial bodies glowing faint in the day.

The guilt will come later, he knows, but for now, he cleans the two of them up, purges himself of all thoughts of _before_ , and tucks her against his side.

"Seteth," she says, and it's more musical than anything he's heard since the beginning of this long night.

If dawn is tempted to break, who is he to stop it?

**Author's Note:**

> i'm on twitter!! @kingblaiddyd for fic updates/general shitposts


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